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SubjectRe: [PATCH v8 7/8] genirq/msi: map/unmap the MSI doorbells on msi_domain_alloc/free_irqs
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On 28/04/16 09:22, Eric Auger wrote:
> This patch handles the iommu mapping of MSI doorbells that require to
> be mapped in an iommu domain. This happens on msi_domain_alloc/free_irqs
> since this is called in code that can sleep (pci_enable/disable_msi):
> iommu_map/unmap is not stated as atomic. On msi_domain_(de)activate and
> msi_domain_set_affinity, which must be atomic, we just lookup for this
> pre-allocated/mapped IOVA.
>
> Signed-off-by: Eric Auger <eric.auger@linaro.org>
>
> ---
> v7 -> v8:
> - new percpu pointer type
> - exit from the irq domain hierarchy parsing on first map/unmap success
> - reset desc->irq to 0 on mapping failure
>
> v7: creation
> ---
> kernel/irq/msi.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 79 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/irq/msi.c b/kernel/irq/msi.c
> index 72bf4d6..d5f95e6 100644
> --- a/kernel/irq/msi.c
> +++ b/kernel/irq/msi.c
> @@ -14,6 +14,8 @@
> #include <linux/irq.h>
> #include <linux/irqdomain.h>
> #include <linux/msi.h>
> +#include <linux/msi-iommu.h>
> +#include <linux/iommu.h>
>
> /* Temparory solution for building, will be removed later */
> #include <linux/pci.h>
> @@ -322,6 +324,56 @@ int msi_domain_populate_irqs(struct irq_domain *domain, struct device *dev,
> }
>
> /**
> + * msi_handle_doorbell_mappings: in case the irq data corresponds to an
> + * MSI that requires iommu mapping, traverse the irq domain hierarchy
> + * to retrieve the doorbells to handle and iommu_map/unmap them according
> + * to @map boolean.
> + *
> + * @data: irq data handle
> + * @map: mapping if true, unmapping if false
> + */
> +static int msi_handle_doorbell_mappings(struct irq_data *data, bool map)
> +{
> + for (; data; data = data->parent_data) {
> + struct device *dev =
> + msi_desc_to_dev(irq_data_get_msi_desc(data));
> + struct irq_chip *chip = irq_data_get_irq_chip(data);
> + const struct irq_chip_msi_doorbell_info *dbinfo;
> + struct iommu_domain *domain;
> + phys_addr_t __percpu *db_addr;
> + dma_addr_t iova;
> + int ret = 0, i;
> +
> + domain = iommu_msi_domain(dev);
> + if (!domain)
> + continue;
> +
> + if (!chip->msi_doorbell_info)
> + continue;
> +
> + dbinfo = chip->msi_doorbell_info(data);
> + if (!dbinfo)
> + return -EINVAL;
> +
> + for (i = 0; i < dbinfo->nb_doorbells; i++) {
> + db_addr = per_cpu_ptr(dbinfo->percpu_doorbells, i);
> + if (map) {
> + ret = iommu_msi_get_doorbell_iova(domain,
> + *db_addr,
> + dbinfo->size,
> + dbinfo->prot,
> + &iova);
> + if (ret)
> + return ret;
> + } else
> + iommu_msi_put_doorbell_iova(domain, *db_addr);
> + }
> + break;
> + }
> + return 0;
> +}

I'm really not fond of this whole loop. Could you try to decouple the
irq_data parsing (looking for a msi_doorbell_info method) from the
actual mapping/unmapping? This would make it a lot more readable.
Something along the lines of:

struct device *dev;
struct irq_chip *chip;
struct iommu_domain *domain;
const struct irq_chip_msi_doorbell_info *dbinfo;

while (data) {
dev = msi_desc_to_dev(irq_data_get_msi_desc(data));
domain = iommu_msi_domain(dev);
if (!domain)
continue;

chip = irq_data_get_irq_chip(data);
if (chip->msi_doorbell_info)
break;

data = data->parent;
}

if (!data)
return 0;

dbinfo = chip->msi_doorbell_info(data);
if (!dbinfo)
return -EINVAL;

[... handle mapping/unmapping here ...]

> +
> +/**
> * msi_domain_alloc_irqs - Allocate interrupts from a MSI interrupt domain
> * @domain: The domain to allocate from
> * @dev: Pointer to device struct of the device for which the interrupts
> @@ -352,17 +404,26 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
>
> virq = __irq_domain_alloc_irqs(domain, virq, desc->nvec_used,
> dev_to_node(dev), &arg, false);
> - if (virq < 0) {
> - ret = -ENOSPC;
> - if (ops->handle_error)
> - ret = ops->handle_error(domain, desc, ret);
> - if (ops->msi_finish)
> - ops->msi_finish(&arg, ret);
> - return ret;
> - }
> + if (virq < 0)
> + goto error;
>
> for (i = 0; i < desc->nvec_used; i++)
> irq_set_msi_desc_off(virq, i, desc);
> +
> + for (i = 0; i < desc->nvec_used; i++) {
> + ret = msi_handle_doorbell_mappings(
> + irq_get_irq_data(virq + i), true);

Do not be afraid of longer lines. Or if you are, create an intermediate
variable. But this kind of construct makes my brain work harder, and I
hate the feeling... ;-)

> + if (ret)
> + break;
> + }
> + if (ret) {
> + for (; i >= 0; i--)
> + msi_handle_doorbell_mappings(
> + irq_get_irq_data(virq + i), false);
> + irq_domain_free_irqs(virq, desc->nvec_used);
> + desc->irq = 0;
> + goto error;
> + }
> }
>
> if (ops->msi_finish)
> @@ -377,6 +438,13 @@ int msi_domain_alloc_irqs(struct irq_domain *domain, struct device *dev,
> }
>
> return 0;
> +error:
> + ret = -ENOSPC;
> + if (ops->handle_error)
> + ret = ops->handle_error(domain, desc, ret);
> + if (ops->msi_finish)
> + ops->msi_finish(&arg, ret);
> + return ret;
> }
>
> /**
> @@ -396,6 +464,9 @@ void msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
> * entry. If that's the case, don't do anything.
> */
> if (desc->irq) {
> + msi_handle_doorbell_mappings(
> + irq_get_irq_data(desc->irq),
> + false);
> irq_domain_free_irqs(desc->irq, desc->nvec_used);
> desc->irq = 0;
> }
>

Thanks,

M.
--
Jazz is not dead. It just smells funny...

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